The use of electro-optical materials such as, for example, Cadmium Telluride crystals, to modulate optical waves is now well known. For example, the changes in the index of refraction produced by changes in the magnitude of an electric field applied to the material through which the light to be modulated passes, can be used to produce changes in, among other things, the polarization of the light. One of many applications for this piezoelectric effect is an electro-optical modulator shutter. More specifically, light in one polarization from a CW laser oscillator may be directed through the crystal with an applied pulsed electric field to alternately rotate the direction of polarization of light passing through it. If the crystal output has a 90.degree. polarization difference depending on whether the electric field is applied, and a polarizer having an orientation equal to one of the two possible outputs is positioned at the output of the crystal, the result is a series of pulses related to the waveform of the applied electric field. In many applications such as, for example, a system wherein the scattered light from radiated pulses is detected for doppler shift, the modulator shutter technique has advantages over a pulsed laser oscillator because the degree of coherence of the light is higher using a shutter. One characteristic of an electro-optical modulator is that the piezoelectric effect in the crystal resulting from the applied electric field causes an acoustic wave which continues in the crystal well after the electric field is removed. The result is an unwanted transmission through the crystal during the time the radiation is supposed to be completely blocked. This continued oscillation of the output is commonly referred to as ringing and it may exist in modulators other than the electro-optical type. In some applications such as, for example, laser radars, the ringing is very damaging because it continues during that time when signal returns of interest are received. A certain part of the ringing output is back-scattered from output optics and is combined with the returns.
Prior art attempts to suppress the ringing effect in electro-optic devices have involved utilizing electro-optic crystals of an irregular shape in order to alter the acoustic resonance characteristics of the crystal, mechanically clamping the crystal with sufficient pressure to prevent it from responding to an applied field at its resonant frequencies, and bonding the crystal to a material having high acoustic energy absorption properties. These schemes have not achieved sufficient ringing suppression for certain particular applications.